Genealogists rely on multiple sources to document a family tree.
One source does not give all of the facts – so researchers must look at multiple family history records to gather the details for each family.
For example – James Edwin Ayres (1817-1893) and his wife Ann (Ford) Ayres (1817-1901) are listed in the 1850 census for Greenburgh, Westchester County, New York. 
TIP: You may search the census for free at FamilySearch.org
On closer inspection we see that there is an age gap between the children.
Sarah Ayres – born about 1844
and Frederica Ayres born about 1849
It appears that there might be another child that was probably born in 1846 and who died before 1850.
A quick search of GenealogyBank shows that was the case. 
In the Hudson River Chronicle (Sing Sing, New York) – 12 December 1848 we find an obituary notice for Lovina Ayres stating that she was born 7 August 1846 and died 26 November 1848.
TIP: Newspapers are essential for finding and documenting every person on your family tree.
Search the census for free at FamilySearch.org
.